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VIDEO WORLD
Getting
the
I
sat in on a product demonstration for a
projector the other day. While the projector
was impressive in terms of brightness,
noise level, and ease of set up and operation, I
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was not impressed with the image. It seemed
a bit fuzzy. The material on-screen was a rather
generic slide show, and the projector had
been set up and focused properly. Then I realized
what the problem was. It wasn’t the content
or the projector, but the fact that the projector
and computer were at different screen
resolutions. I mentioned this to the rep, who
very quickly reset his laptop so that they
were matched and the image was improved
dramatically. It was a pixel for pixel match to
what the computer was putting out.
Video scalers can be both a blessing and a
curse — often at the same time. While a scaler
will allow us to adjust the input resolution or
even the format to match a specific output
format, it does not guarantee our image quality.
As a result, what may look beautiful on the
local monitor may look bad projected on a display—the
kind of bad that clients remember.
So what are these resolutions and how do
we get a handle on them?
I have said before that I believe that projectors
will plateau at a resolution of 1080 for
a while because of the HD standard and because
it will
give the market
a chance
to catch
up. But interestingly
enough, projectors
have
only recently
come out
with resolutions
of 1080
pixels. Most
p r o j e c t o r s
topped out
at SXGA+,
giving them
1050 pixels.
So what
happens to
those other
30 lines of
information?
Common aspect ratios and corresponding screen resolutions.
They get
lost in the scaling. They can either be thrown
out and part of the image is cut off, or they
get squeezed in and the image has this very
slight fuzzy appearance where it occurs. On
an SXGA+ screen trying to reproduce a 1080
image, the distortion is slight and often unnoticed
except by a trained eye.
What about all those other resolutions
out there? What are we supposed to do about
them? Oversized images can be reduced to
fit on screen although it is just reducing the
image size by throwing out pixels until it fits.
This is where scaling can be a blessing or a
curse. How the scaler eliminates pixels to produce
the final image determines the quality
of the finished product. If it is done smoothly
and evenly, the image will still look good
when it is done. If it is done poorly, the image
will either look cropped (if we’re lucky) or it
will look like the vertical and/or horizontal
clocks are out of phase. Has your computer
monitor ever looked like part of the verticals
on the lettering was missing, but when you
reset the screen resolution it all came back
By Paul J. Duyree
properly? That’s what I am talking about.
The other place that scaling helps and
hurts us is with screen format. If we use an
SXGA (not plus) projector, we give up not only
26 pixels of vertical resolution, we also surrender
400 pixels of horizontal resolution. If we
feed this projector a 1080 signal, it will get
squashed big time before it hits the screen.
All of the major and most of the minor
projector manufacturers have taken care
to install good quality scalers onboard their
projectors. Still, just like in audio world, there
are a number of even better quality outboard
scalers that do amazing jobs of helping us get
our images under control. I hope to review a
few of these in the coming months.
The other side of the scaling issue is taking
smaller images and enlarging them to fill
the screen. If you are doing a presentation
and the source material is originally SVGA
(800x600) or even XGA (1024x768), it will have
to be scaled up to fill the screen.
As the image is stretched to fill the screen,
the scaler has to extrapolate between two
pixels or two lines and calculate how to fill the
missing information. Our new image is going
to blur a bit or look pixilated (sometimes
called tiled or mosaic). There is no simple solution
to this other than to recreate the source
material in the proper resolution. An alternative
way to get around the scaling issue is to
convert the image to a standard (SVGA) or
high def (XGA) video signal and then process
and project it.
Next month we will look at these resolutions
and what they mean on screen in terms
of quality and size. In the meantime, enjoy
what is left of summer.
Paul J. Duryee is the systems design lead at
Maxx Technology. He recently got his hair cut. He
can be reached/ridiculed at pduryee@plsn.com
46 PLSN AUGUST 2006
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